Hydrocarbon products such as oil and natural gas are generally extracted from wells drilled into the earth. One aspect of drilling such wells is known as “completion.” Completion is the process of making a well ready for production or injection. There are several techniques to complete a well. Such techniques generally involve lining the well with casing, and cementing the casing in place.
Cementing operations begin by pumping cement down into casing and back up through the annulus between the casing and the wall of the wellbore. After filling the annulus with cement, an operator typically wipes the wellbore by pumping a wiper device such as a wiper plug, dart, or ball through the casing. The wiper device is designed as a barrier to prevent cement contamination with displacement of wellbore fluids as well as to “wipe” excess or superfluous cement from the string.
After cementation, the wellbore is reopened downhole to allow circulation of fluids to continue the completion process. In some cases, this is done using a downhole tool known as a “toe valve” or an “initiation valve.” However, in some instances, the toe valve may fail to open and can block circulation. One factor that plays a role in these failures is cement left behind in the toe valve that the cement wiper plug did not remove.